Recording and reproduction of impulses



April 3 E. w. KELLOGG 3 RECORDING AND REPRODUCTION OF IMPULSES Filed March 9, 1935 INVENTOR [DIV/4RD W KLL066 7k g/W ATTORN EY Patented Apr. 23, 1935 UNITED STATES RECORDING AND REPRODUCTION or IMPULSES Edward W. Kellogg. Moorestown, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application March 9, 1933, Serial No. 660,159

'Z Claims. (01. 211-23) This invention relates to the recording and reproduction of impulses such as those of audiofrequency, and has for its principal object the provision of an improved apparatus and method of operation whereby the film or other record surface is given a smooth and uniform movement at the translation point where the impulses are recorded or reproduced.

In the recording or reproduction of sound, when the record consists in a long flexible strip of material, such as a motion picture film for example, one method of insuring substantially constant velocity is to employ a cylinder which is caused to' rotate at uniform speed and to cause the record to be held sufiiciently firmly against the cylinder so that it will not slip. Adequate pressure between the cylinder or drum and the record is sometimes secured by tension on the record but a more positive means of insuring sufiicient friction between the two is to employ one or more auxiliary rollers which press the record against the uniformly rotating drum. Such pressure rollers may be provided with yielding tires, of rubber for example.

If the record is subjected to a moderate degree of tension, there is usually little difiiculty in causing it to remain snugly against the drum throughout the angle of wrap. It is very desirable, however, in certain constructions to minimize the tension on the record and under these conditions, although a pressure roller such as has been described may prevent tangential slipping 0f the record with respect to the drum, the record may not remain firmly in contact with the drum at all times at points within the are of wrap which are not directly under the pressure rollers. v

In some devices the record is pulled past the point where recording or reproduction takes place and is guided and supported at the said point, for example, a stationary gate. It may be suificient in such devices to insure that the record move uniformly at the one point where it is pinched between the drum and the pressure roller. A common construction, however, is to effect the recording or reproduction at a point where the film is actually supported by the uniformly rotating drum. Under these conditions it is especially important that the record remain definitely in contact with the drum at the recording or reproduction point. If the record is made photographically and reproduced optically, there is nothing in contact with the film at the recording or reproduction point to hold the film against the drum and any failure of the record to stay against the drum will mean that he optical system will be out of focus.

In order that vibrations of the record, due, for example, to the action of sprocket teeth which engage the record, may not cause vibrations of the record where it should be in firm contact with the drum, it may be desirable to employ two pressure rollers. This successfully isolates the portion of the film between the two pressure rollers. It sometimes happens, however, that a slight loop of excess length of film accumulates between the two pressure rollers, especially as has been stated if the film is not under appreciable tension. The purpose of my invention is to prevent the formation of such a loop between the pressure rollers.

If the pressure roller, where the record is fed on to the drum, exerts a slight retarding force on the record due, for example, to friction in the pressure roller bearings, this has an effect similar to tension on the film and'helps to keep it tight around the drum. There is objection, however,

to the application of any more retarding force than necessary, because the application of any frictional forces increases the difliculty of in-- suring uniform rotation of the drum. My invention provides means whereby a suflicient retarding force may be applied against the record but the mechanical work taken up by the pressure roller at this point is in a large measure returned to the drum through a second connection. 7 Thus the retardation of the drum is considerably less than would be the case if the same amount of retarding force were applied at the record and the force were absorbed entirely in ordinary bearing frictionor by means of a brake.

In the case of the pressure roller where the record leaves the drum, which I shall hereinafter callthe second pressure roller, it is desirable that the roller exert a forward force on the record. This may be accomplished by means of an auxiliary driving system such as shown in my figures. Instead of the roller rotating on a stationary shaft, it is mounted on a sleeve which is driven at higher speed than that at which the roller itself runs. This sleeve may be driven in any suitable manner but, the purpose may be most simply accomplished by means of friction coupling or gearing to the drum shaft. In this construction the friction between the roller and the sleeve provides the desired forward torque but it is obvious that-said torque might be supplied through other forms of friction coupling between the roller and a member rotating at higher speed. If the power fordriving the second pressure roller is obtained from the rotation of the drum itself,

through the contact between the pressure roller tire and the record.

I regard the supplying of a forwardforce by the a second pressure roller as of more importance than the provision ofadditional retarding force by the first pressure roller for the reason that the first pressure roller, even though mounted in the usual way, will always apply a slight retarding force to the record. It is evident that the combined eflect of the backward tangential force at the point of contact at the first pressure roller and the forward force at the point of con tact with the second pressure roller is to sub ject the film between the two rollers to a slight tension, thereby insuring that the record will stay snugly against the drum throughout the intervening arc.

The invention will be better understood from the following description when considered in connection with the accomp nying drawing and its scope will be pointed out in the appended claims.

Referring to the drawing,

Figs. 1 and 2 illustrate end and sectional views of a film gate wherein both the pressure rollers are driven,

Figs. 3 and 4 illustrate a modification wherein only the roller at the point where the film leaves the drum is driven, and

Fig. 5 illustrates an embodiment wherein both the rollers are driven through an idler gear mounted on the drum shaft.

The form of apparatus illustrated by Figs. 1 and 2 includes a drum l mounted at the end of a rotatable shaft ll. Asshown more clearly in Fig. 1, a film or other record strip l2 passes around the drum under the control of a pair of pressure rollers l3 and I4 supported respectively by means of arms l and I6 or by other suitable means. Each of these rollers is provided with a frictional bearing surface I! in order to permit their peripheries to move at the same speed as the film irrespective of the fact that they tend to be driven at different speeds. In the apparatus of Figs. 1 and 2, the roller I3 is driven through a frictional disk It and a frictional surface I 9 formed on the end of the drum l0 and the roller I4 is driven through a friction disk 20 and a frictional surface 2lformed on the end of the drum III.

Under these conditions, movement is imparted to the film I! by rotation of the drum III, the rollers I 3 and I tend to be driven respectively a little slower and a little faster than the peripheryofthedrum,andthefilmisatalltimessubiected to a tension which maintains it in close contact with the drum surface, thus insuring that it will remain in'focus at the recording or reproducing point 22. I

It will be apparent that this type of gate may form a part of a photographic recorder or reproducer or a part of a mechanical or electromechanical recorder or reproducer. In the arrangement of Fig. 1 it is shown as applied to a photographic recorder wherein suitably modulated light is applied to the film I2 at the translation point 22 through an optical system 23. In the case of a photographic reproducer, a constant beamoflightisofcoursepassedthroughthefilm to a light sensitive cell which may be supported zvithiniithedrmnbymeansofastationary armor he e.

. In the case of mechanical or electromechanical recording and reproducing employing a grooved record in the form of a tape or film, the optical system is replaced by a suitable cutter or pickup device, and this invention serves the purpose of applyingtension to the film at the point of translation.

It is sometimes sufficient that only one of the pressure rollers be driven. In the modification of Figs. 3 and 4, the roller 14 is driven through the friction pulleys 20 and 2| in the manner previously described and the roller I3 operates as an idler with some friction at its bearing.

As indicated by Fig. 5, the rotation of the rollers I3 and I4 may be controlled by means of an idler gear 24 interposed between gears 25 and 26 mounted respectively on the shafts of the rollers l3 and I4. With this construction, the forward pull of the roller I4 is balanced against the backward, pull of the roller l3 and film is stretched snugly around the drum l0 as previously explained. The power required to supply the forward torque to the second pressure roller I4, is in the case of Fig. 5 derived from the first pressure roller I 3, instead of directly from the drum as in Figs. 1 to, 4. With the construction shown in Fig. 5, it is unnecessary to provide sliding surfaces I! in both rollers l3 and II, and if only one such surface is provided, I prefer that it should be in the second pressm'e roller I4, the roller l3 and gear 25 being operatively integral.

In case it is found that the bearing surface I! does not provide. sufilcient friction to impart as much forward torque to the rollen H as is desired, adjustable brake means may be provided acting between roller M and gear 26, to increase the friction coupling between the two, but I have not found this measure necessary, sufiicient friction being afforded by moderately small bearing clearance and the employment of a stifi lubricant.

I claim:

1. A record moving apparatus including a member provided with a record support surface, a roller for maintaining said record in contact with said surface, means tending to impart to the peripheral surface of said roller a speed which differs from that of said support surface, and means for causing said surfaces to be moved at substantially the same speed.

2. A record moving apparatus including a member provided with a record support surface, a roller for maintaining said record in contact with said surface, means tending to impart to the peripheral surface of said roller a speed which differs from that of said support surface, and means including a frictional bearing for permitting said surfaces to be moved at substantially the same aw d 3. A record moving apparatus including a rotatable drum, a roller for maintaining said record in engagement with said drum, means tending to impart to said roller a peripheral s of that of said record, and a frict onal bearing for said roller whereby slippage between said record and said roller is obviated.

4. A record moving apparatus includinga rotatable drum, a roller for maintaining said record in engagement withsaid drum, means tending to impart to said roller a peripheral speed somewhat lower than that of said record, and a frictional bearing for said roller whereby slippage between said drum and said record is obviated.

5. A record moving apparatus including a ro tatable drum, a pair of rollers for maintaining said record in engagement with said drum, means inexcess tending to impart to said rollers peripheral speeds which are respectively somewhat lower and somewhat higher than that of said drum, and frictional bearing means for permitting the peripheries of said drum and said rollers to be moved at substantially the same speed.

6. A record moving apparatus including a rotatable drum, a'pair of rollers for maintaining said record in engagement with said drum, means including an. idler gear tending to impart to said rollers peripheral speeds which are respectively somewhat lower and somewhat higher than that of said record, and-frictional bearings for pre- 

